Process for producing acrylic acid esters



United States Patent Of 3,035,086 PROCESS FOR PRODUCING ACRYLIC ACIDESTERS Jesse T. Dunn, Charleston, W. Va., assignor to Union CarbideCorporation, a corporation of New York No Drawing. Filed Mar. 23, 1959,Ser. No. 800,941 4 Claims. (Cl. 260-486) This invention relates to theproduction of acrylic acid esters. More particularly it is concernedwith new catalysts for carrying out the interaction of acetylene, carbonmonoxide and an alcohol to produce acrylic acid esters.

It is well known that acrylic acid and its esters can be produced by thereaction of acetylene and carbon monoxide with compounds having areplaceable hydrogen, such as water, alcohols, carboxylic acids, ammoniaand amines, in the presence of a metal carbonyl catalyst, or othercatalysts such as the complex triphenylphosphinenickel halide compoundsor the complex nickel halidequarternary ammonium compounds.

It has now been found that the complex combinations obtained by theadmixture of a nickel halide with an unsaturated organic heterocycliccompound which has a ring carbon atom doubly bonded to a nitrogen atomforming part of the heterocyclic ring structure and singly bonded to thenitrogen atom of an imino radical (=NR) or a sulfur atom also formingpart of the heterocyclic ring structure and to a mercapto radical (SH)not in the ring are excellent catalysts for the production of acrylicacid esters. The suitable organic heterocyclic compounds contain one ofthe groups:

SHR

N=C-S in the ring structure.

The unsaturated organic heterocyclic compounds useful in this inventionare the Z-benzinddazolethiols:

R N-R R \N//--SH and the l,3,4-thiadiazoles-2-thiols:

wherein R represents a hydrogen atom or a hydrocarbyl radical, which isa radical containing hydrogen and carbon atoms only, such as an alkylradical containing up to about 12 carbon atoms, for example, methyl,ethyl, isopropyl, n-butyl, tert.-butyl, Z-ethylhexyl, decyl, dodecyl,and the like, or an aral-kyl radical, for example, benzyl, phenethyl,and the like, or a cycloalkyl radical, for example, cyclopentyl,cycloheptyl, and the like, or an aryl radical, for example, phenyl,naphthyl, and the like, or an alkaryl radical, for example, tolyl,xylyl, and the like; R represents a hydrogen atom, a hydrocarbyl radicalas defined above or an amino radical; and R" represents a hydrogen atom,a hydrocarbyl radical as defined above or a mercapto radical.

Illustrative of the compounds which can be used in this invention are7-amino-2-benzimidazolethiol, 3-methyl-Z-benzimidazolethiol,2-:benzimidazolethiol, 5-propyl-2- benzimidazolethiol, 5 phenyl 2benzimidazolethiol, 5- tolyl-Z-benzimidazolethiol,5-benzyl-Z-benzimidazolethiol,

3,035,086 Patented May 1 5, 1962 5 cyclohexyl 2 benzimidazolethiol,1,3,4-thiadiazole-2- thiol, S-methyl-1,3,4-thiadiazole-2-thiol,5-phenyl-l,3,4- thiadiazole-Z-thiol, 1,3,4-thiadiazole-2,5-dithiol, andthe like.

The catalyst complexes suitable for use in this invention are preparedby admixing a nickel halide, such as nickel bromide, nickel chloride,nickel fluoride and nickel iodide, with one or more of the above-definedZ-benzimidazolethiols or l,3,4-thiadiazoles-2,5-dithiols. In preparingthe catalyst complex the order of addition of the two components is notcritical. Thus, the organic heterocyclic compound can be added initiallyto the alcohol reactant to be used in producing the acrylic acid ester,followed by the nickel halide component, or the reverse order ofaddition can be followed. The acrylic acid esters are then produced bythe interaction of acetylene with carbon monoxide and the alcohol atelevated temperature and under increased pressure in the presence of acatalytic amount of the catalyst complex. The use of the catalystcomplexes of this invention results in a high ratio of monomer topolymer. 1

The starting alcohols are preferably the aliphatic monohydroxy saturatedalcohols and ether alcohols having up to about 22 carbon atoms andpreferably from 1 to about 12 carbon atoms in the molecule. Illustrativealcohols are ethanol, isopropanol, tertiary butanol, pentanol, 2-ethylhexanol, dodecanol, ethylene glycol monomethyl ether, ethyleneglycol monoethyl ether, ethylene glycol monobutyl ether, and the like.

The reaction is successfully carried out with the catalyst complexes ofthis invention at temperatures of from about C. to about 250 C. orhigher. Temperatures of from about C. to about 200 C. are preferred. Thereaction can be expedited by the use of slight pressures, and we preferto operate at pressures exceeding about 100 p.s.i.g., with pressures offrom about 400 p.s.i.g. to 500 p.s.i.g. most preferred. Higher pressuresup to about 4000 p.s.i.g. to 5000 p.s.i.g. can be used with properprecautions.

The mole ratio of nickel halide to unsaturated organic heterocycliccompound can be varied over wide limits and does not appear to becritical; nevertheless, we prefer to employ about equimolar amounts ofeach component. The total amount of catalyst complex charged to thereaction mixture is not critical and can be varied over a Wide range, solong as a catalytic amount is present. When based on the alcoholcharged, it has been found that a catalyst complex containing about0.0622 mole each of the nickel halide and the organic heterocycliccompound per 16 moles of alcohol yields the highest conversions from aneconomical viewpoint. Higher concentrations of catalyst give a fasterreaction but at greater cost; while lower concentrations, though moreeconomical, result in lower productivity.

The reaction can be carried out in a batchwise manner or in a continuousmanner by methods which are known to the art. The acetylene and carbonmonoxide can 'be added separately, or for reasons of safety, as amixture of gases, which mixture can be widely varied.

The following examples further serve to illustrate this invention. Partsare by weight unless otherwise specified.

Example 1 A three-liter stainless steel rocking autoclave was chargedwith 740 grams of ethanol, 5.6 grams of mercuric bromide and 9.6 gramsof butyl bromide. Then 6.8 grams of nickel bromide and 5 grams of7-amino-2- benzi-rnidazolethiol were added to prepare the catalystcomplex and the autoclave was sealed and purged, first with carbonmonoxide and then with a 1:1 mixture, by volume, of acetylene and carbonmonoxide. The autoclave was rocked and the pressure was increased toabout a 40 psig. by the further addition of acetylene-carbon monoxidemixture. The gas addition was stopped and the autoclave was heated to100 C., at which time the pressure was increased 25 p.s.i.g. by theaddition of acetylene. The total pressure was then increased to about300 p.s.i.g. with the acetylene-carbon monoxide mixture, and heating wascontinued to a temperature of about 150 C. At this point the pressurewas increased to 450 p.s.i.g. and maintained between 400 p.s.i.g. and450 p.s.i.g. by the periodic addition of acetylene-carbon monoxidemixture for 4.3 hours. During this period the temperature was keptbetween 157 C. and 166 C. The reaction was stopped by aircooling theautoclave and then releasing the pressure. The reaction mixture wasfiltered to remove solid materials and the filtrate was distilled toseparate monomeric ethyl acrylate, most of which distilled as the ethylacrylate-ethanol azeotrope, from the higher boiling acrylate esters andpolymer-containing residue. The total yield of ethyl acrylate Was 436grams.

In a similar manner 2-ethylhexyl acrylate is prepared by substitutingZ-ethylhexanol for ethanol.

Example 2 In the manner described in Example 1, 740 grams of ethanol wastreated with acetylene and carbon monoxide at 150 C. to 180 C. over a6.3 hour period in the presence of a catalyst complex prepared from 6.8grams of nickel bromide and 4.6 grams of 1,3,4-thiadiazole-2,5- dithiol.The total yield of ethyl acrylate was 337 grams.

In a similar manner butyl acrylate can be prepared by substitutingbutanol for ethanol; and in the presence of a catalyst complex preparedfrom nickel bromide and 5- methyl-1,3,4-thiadiazole-2-thiol.

What is claimed is:

1. In the manufacture of an acrylic acid ester by the reaction ofacetylene with carbon monoxide and an alcohol at elevated temperatureand under increased pressure, the improvement which comprises carryingout said reaction in the presence of a catalyst complex of a nickelhalide and an unsaturated organic heterocyclic compound selected fromthe group consisting of 2-benzimidazolcthiols of the general formula:

4 and 1,3,4-thiadiazole-2-thiols of the general formula:

El J-sn wherein R represents a member selected from the group consistingof hydrogen and a 'hydrocarbyl radical selected from the groupconsisting of an alkyl radical containing up to 12 carbon atoms, anaral-kyl radical selected from the group consisting of benzyl andphenethyl, a cycloalkyl radical containing from 5 to 7 carbon atoms inthe ring, an aryl radical selected from the group consisting of phenyland naphthyl, and an alkaryl radical selected from the group consistingof tolyl and xylyl; R represents a member selected from the groupconsisting of hydrogen, a hydrocarbyl radical as defined above for R,and an amino radical; and R" represents a member selected from the groupconsisting of hydrogen, a hydrocarbyl radical as defined above for R,and a mercapto radical.

2. A method as claimed in claim 1, wherein the reaction is carried outin the presence of 7-arnino-2-benzimidazolethiol as the organicheterocyclic compound.

3. A method as claimed in claim 1, wherein the reaction is carried outin the presence of 1,3,4-thiadiazole-2,5- dithiol as the organicheterocyolic compound.

4. A method as claimed in claim 1, wherein the reaction is carried outin the presence of 5methyl-1,3,4-thiadiazole-Z-thiol as the organicheterocyclic compound.

References Cited in the file of this patent UNITED STATES PATENTS2,737,484 Passal Mar. 6, 1956 2,768,968 Reppe et al. Oct. 30, 19562,806,040 Reppe et al. Sept. 10, 1957 2,809,976 Reppe et al. Oct. 15,1957 2,854,458 Reppe et al Sept. 30, 1958 2,881,176 Hogsett Apr. 7, 19592,886,591 Lautenschlager et al. May 12, 1959

1. IN THE MANUFACTURE OF AN ACRYLIC ACID ESTER BY THE REACTION OFACETYLENE WITH CARBON MONOXIDE AND AN ALCOHOL AT ELEVATED TEMPERATUREAND UNDER INCREASED PRESSURE, THE IMPROVEMENT WHICH COMPRISES CARRYINGOUT SAID REACTION IN THE PRESENCE OF A CATALYST COMPLEX OF A NICKELHALIDE AND AN UNSATURATED ORGANIC HETEROCYCLIC COMPOUND SELECTED FROMTHE GROUP CONSISTING OF 2-BENZIMIDAZOLETHIOLS OF THE GENERAL FORMULA: